... red, green, blue, purple, brown, and black; but red is by far the more common color. Luster ... 2/m Crystal Habits include the typical octahedron, but can be found as dodecahedrons and combinations of other ... . Spinel also comes in beautiful blue tones called cobalt spinel, but these are very, very rare.Because spinels ... being too rare can be a drawback because so few people even get a chance to develop a ...